Measuring muscle tone with isokinetic dynamometer technique in stroke patients

Abstract

Summary Study aim: Increased muscle tone, a common consequence of stroke, has neural and non-neural components. Spasticity is related to the neural component. Non-neural resistance arises from passive stiffness. This study was designed to assess the feasibility of using isokinetic dynamometry to evaluate wrist flexor muscle spasticity in stroke patients. Materials and methods: Twenty-six patients with hemiplegia in the subacute phase of stroke participated in this study. An isokinetic dynamometer was used to stretch wrist flexor muscles at four velocities of 5, 60, 120 and 180°/s on both the paretic and non-paretic sides. Peak torque at the lowest speed (5°/s) and reflex torque at the three higher speeds were quantified. Peak torque at the lowest speed was attributed to the non-neural component of muscle tone, and was subtracted from the torque response at higher velocities to estimate reflex torque (spasticity). Data from the two sides were compared. Results: There was no significant difference in peak torque between the paretic (2.47 ± 0.22 N·m) and non-paretic side (2.41 ± 0.28 N·m) at the lowest velocity of 5°/s (p=0.408). However, compared to the non-paretic side, the paretic side showed higher reflex torque (p<0001), and reflex torque increased rapidly with increasing velocity (p < 0.05). Conclusion: The isokinetic dynamometer distinguished spasticity from the non-neural component and showed higher reflex torque on the paretic side compared to the non-paretic side. This instrument is potentially useful to assess the efficacy of therapeutic interventions aimed at modifying spasticity.